It is generally known to provide an impervious inner liner inside of a woven fabric cargo bag in order to protect the contents from invasion by water and the like. For example, U.S. Pat. No. 4,596,040 discloses an inner impervious plastic liner positioned within and generally conforming to an outer cargo bag formed of woven flexible material. However, this patent provides no means for attaching the liner to the cargo bag so that it is difficult to insure that the liner will conform to the configuration of the cargo bag when being filled with granular material or the like.
U.S. Pat. No. 3,961,655 also discloses a plastic liner positioned inside of a cargo bag of woven flexible material and being attachable to the upper filling skirt of the cargo bag, without attachment of the sides of the liner to the inside surface of the cargo bag. The liner of this patent is also difficult to maintain in conforming condition with the outer bag while being filled with granular material.
In an attempt to overcome the deficiencies of the inner liners in the cargo bags disclosed in these two prior patents, U.S. Pat. No. 4,597,102 discloses an inner liner for a cargo bag in which each of the four corners of the inner liner are provided with outwardly extending tabs. These tabs are sewn into seams formed along each corner of the outer cargo bag. While the inner liner of this patent is maintained in conforming condition to the outer bag during filling with granular material, the inner liner of this patent cannot be easily removed therefrom so that the cargo bag can be used without the inner liner in position.
U.S. Pat. No. 4,658,989 discloses an impervious inner liner which is provided with spaced-apart pressure-sensitive adhesive spots for adhering the outer surface of the inner liner to the inner surface of the cargo bag when the liner is inflated. Strings or lines are attached to the spots of the pressure-sensitive adhesive and extend outwardly through the open top of the bag so that the flexible inner liner can be removed from the cargo bag after the granular material has been discharged from the bag. However, the pressure-sensitive spots on the outer surface of the liner make it difficult to insert the inner liner into the cargo bag. Also, the mechanism required to inflate the inner liner to cause the pressure-sensitive adhesive spots to stick to the inner walls of the bag is not always readily available and further complicates the process of inserting the inner liner into the bag.